Acute Bacterial Arthritis in Children: Guidelines From the Pediatric Infectious Diseases Society and Infectious Diseases Society of America

Acute bacterial arthritis affects up to 1 in 10,000 children annually. It most often is the result of hematogenous spread to a synovial joint such as the knee, ankle, elbow, or shoulder. The hip is the most commonly infected, in up to 40% of cases. The knee, ankle, elbow, and shoulder also are commonly infected. Bacterial infection of fibrocartilaginous joints without synovial fluid, such as intervertebral joints, the pubic symphysis, and sacroiliac joints, is rare and difficult to diagnose.

The most common cause of acute bacterial arthritis in children is Staphylococcus aureus. This type of acute bacterial arthritis often manifests with rapid progression of symptoms and is associated with the greatest risk of long-term complications. Kingella kingae can be the infecting organism in children younger than 4 years and causes milder symptoms and an indolent course. The Pediatric Infectious Diseases Society and Infectious Diseases Society of America have published guidelines for evaluation and treatment of suspected acute bacterial arthritis in otherwise healthy children older than 1 month.

It is important to differentiate between acute bacterial arthritis and synovitis due to similar presentation of joint pain. Transient nonbacterial synovitis is the most common cause of acute painful hip in children. It consists of self-limited joint pain and mild inflammation caused by viral synovitis, reactive synovitis, or unrecognized K kingae infection.

Acute bacterial arthritis often presents with joint pain, swelling, erythema, and systemic signs of infection. Joint tenderness and increased pain with movement are common. The clinical presentation of acute bacterial arthritis can vary based on the affected joint, causative bacteria, and patient age.

Initial Laboratory Analyses

A complete blood cell count should be performed in children with suspected acute bacterial arthritis because the white blood cell count tends to be higher in acute bacterial arthritis than transient nonbacterial synovitis. A serum C-reactive protein (CRP) level can be considered on initial evaluation to establish a baseline for sequential monitoring to assess treatment response. Erythrocyte sedimentation rate and serum procalcitonin level do not have roles in initial evaluation because they do not differentiate between bacterial and nonbacterial causes.

Blood culture should be performed for children with suspected acute bacterial arthritis before starting antimicrobial treatment. Although only 20% of children with acute bacterial arthritis have positive results, blood culture is quick to perform, and results can help guide treatment.

Imaging

Plain radiography of the affected joint and adjacent bones is recommended, primarily to identify other causes of joint pain, including fracture, tumor, slipped capital femoral epiphysis, or Legg-Calvé-Perthes disease. Radiography has a sensitivity of 25% for osteoarticular infections.